The present invention relates to a system for lubricating a rear bush (i.e. a rear bushing) disposed adjacent the rear end of an extension housing of an automotive transmission for supporting an output shaft or sleeve yoke splined thereto.
In conventional automotive transmissions, an extension housing is extended rearwardly from a transmission case for supporting an output shaft or sleeve yoke splined thereto by a rear bush disposed adjacent the rear end of the extension housing. The extension housing contains oil for lubricating the rear bush. The rear bush is provided with oil grooves so that lubricating oil flows through the rear bush forwardly and backwardly under the screw pump action produced upon rotation of the output shaft or sleeve yoke in the rear bush, and a plurality of axially extended passages are formed in a rear bush retainer section of the extension housing for intercommunicating the front and rear spaces in front of and behind the rear bush so that sufficient lubricating oil may exist in the rear space as well as the front space.
In general, the automotive transmissions of the type described are mounted on vehicles of the front-engine and rear-drive type at an angle of 3.degree. to 4.degree. inclined rearwardly with respect to the horizontal because of the construction of the vehicles. Therefore the lubricating oil is filled into the extension housing in such a quantity that the inclined rear bush may be completely immersed with lubricating oil. In other words, the rear bush is below the level of the lubricating oil when a vehicle is traveling on a flat road or upgrade slope, but when the vehicle is traveling on a down-hill, the lubricating oil flows toward and remains on the side of the transmission case, leaving almost no lubricant in the rear bush so that seizure of the rear bush results.
The simplest solution for this problem is to increase the lubricating oil in the extension housing so that the rear bush may be kept immersed even during the down-hill traveling, but this method is not preferable because the transmission efficiency decreases with the increase in resistance encountered by the transmission gears from the increased lubricating oil and the power required for shifting the transmission is increased.
To overcome this problem there has been proposed and practised a method for disposing in the extension housing a weir extended upwardly from the bottom thereof so as to hold back the flow of the lubricating oil toward the transmission case during the down-hill traveling, thereby keeping the rear bush sufficiently immersed with the lubricating oil. However this method must be provided with means for trapping the lubricating oil splashed by the transmission gears and feeding the trapped oil to an oil sump defined by the weir. As a result, the parts required for the lubrication of the rear bush is increased in number, and the fabrication of the extension housings by die-casting becomes difficult because the existence of the weir, thus resulting in the use of inefficient sandmolds with a complex pattern and the decrease in productivity.